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Whilst bonsai trees are a fantastic hobby to get to grips with, one of the problems associated with the art of bonsai that I had to deal with is an increase in the number of pests like scale to deal with. Something slightly more worrying I found however is white spots on bonsai leaves, so what exactly is this?
White spots, powder, white film, or mildew on bonsai leaves is a surefire sign that your bonsai has a fungal infection. This is particularly common in broadleaf species like Chinese Elm. To remove, simply wipe down and use fungicide regularly.
So how exactly can you treat your bonsai for white spots? And can white spots be dangerous to your plant? Keep reading to find out more.
Just a quick heads up, over the past three years of running Plantpaladin, hundreds of people have asked for product recommendations. As such, You can find my favorite indoor bonsai tree here (link takes you to Bonsaiboy), my favorite outdoor bonsai tree (link takes you to Bonsaiboy), or have a look at all the products I recommend here.
White spots on bonsai leaves
Whilst a lot of us knew that getting into bonsai would mean a lot of patience and care, the truth is that keeping bonsai will men at some point, sooner or later we will need to deal with infestations.
Whilst I’ve already covered how to deal with scale infestations – (check out this post if you are currently struggling with brown spots on your bonsai,) like children, bonsai trees are also susceptible to more than one infestation and that leads us to a major problem that is all too common.
So what exactly is these white spots on bonsai trees?, well to help summarize I’ve summarised the main points below:
- A white spot or powder-like substance on a bonsai is most commonly associated with a mold or fungal infection on your plant.
- Whilst this most commonly resembles a white powder it can also look like a thin white film, or spots on your tree.
- Most minor infestations of fungus or mold can be treated fairly easily with things like plant fungicide – think of them as an athletes foot spray for your plant
- Another homemade option to treat would be to use something like rubbing alcohol, and soapy water to neutralize the white spots.
- More extreme cases of white spots may need to be taken to a specialist.
Now, this is quite a large topic unto itself so feel free to check out this blog post covering everything around white powder specifically.
What causes white spots on bonsai trees?
Sadly, because bonsai trees are made up of so many different species, it can be very easy for them to suffer from regular fungal and mold infections.
White spots on your bonsai trees are caused by 2 main factors
- In some situations mold
White spots caused by fungus
White spots or powdery mildew are the most common type of white spots that will affect your bonsai. It is caused by a fungus that thrives in dry soil conditions in both damp or dry climates.
These white spots then will typically start on the top of your bonsai leaves and if left unchecked, will typically start to spread to the underside of your bonsai and then to the stems of your plant.
If left unchecked your bonsai leaves will start to turn yellow before turning brown, drying up, and falling off – something we don’t want with bonsai trees!
These white spots, caused by a fungus, can be common in any plant but will especially take hold of younger bonsai or bonsai that are unhealthy – meaning bonsai that you keep indoors will likely be a lot more susceptible.
How to treat white spots on bonsai caused by fungus?
So it’s more likely than not that your bonsai’s white spots are caused by a fungus, so we must treat it as soon as we notice it.
The best option to treat white spots on your bonsai caused by fungus is to use a plant fungicide.
I personally like to use Bioadvanced fungicide (link will take you to Amazon) as not only will it do a fantastic job in getting rid of any fungus, it also acts as an insecticide, helping remove any pesky insects that may be damaging your plant.
To treat white spots effectively it would be best to follow these steps:
- Remove your bonsai from any surrounding plants to ensure the fungus does not spread
- Put on a pair of gloves to avoid getting the antifungal spray on your skin
- Wipe down your bonsai as best you can to remove the top layer of any white spots on your bonsai
- Spray your plant leaves with a fungicide spray, aiming directly for the leaves to ensure a nice even distribution around the leaves.
- Leave your plant for 24 hours then repeat this process once more.
A few sessions of doing this, typically over two weeks, should ensure that your white spots will disappear.
It’s important however that you play this by ear as the fungus will work differently depending on the size and health of your bonsai as well as the plant breed you are working with.
How to treat more serious causes of white spots on your bonsai?
Now whilst using the fungicide should work for most of you if your bonsai is too far gone to the point where your leaves are already discolored and the plant looks like a sad excuse of a bonsai you will need to see a specialist.
Most garden centers have bonsai clinics to address just these problems and will be professionally set up to deal with fungal outbreaks (seriously it’s literally their day job)
So if you have tried fixing the problem yourself to no avail, get in touch with your local garden center.
How to ensure you don’t get white spots on your bonsai?
Once we have successfully treated the white spots on your bonsai, the next step we need to follow is all-around prevention.
To prevent your bonsai from getting white spots again, come up with a routine, where you spray your bonsai with fungicide at least once per week. It’s also important to regularly check for further white powder outbreaks so spend a few minutes every week inspecting your bonsai.
White spots on bonsais are typically caused by dry topsoil or insufficient soil conditions.
If you feel as though your bonsai has poor soil quality consider replacing your soil – check out this post about using cactus soil as a good soil alternative for bonsai.
Regular watering then is essential, so aim to water your bonsai at least once per day and consider also investing in a moisture tray.
Moisture trays in particular can be fantastic options especially if you live in a dry climate – to read up more about this check out my post here.
Another brilliant option to avoid white spots is just to maintain a regular temperature year-round.
Sadly white spots are incredibly resilient growing both in warm and cold climates however, a trick I learned that works is to try and keep a contact temperature to help get your bonsai adjusted.
Greenhouses typically work best for this.
“Most white spots on bonsai trees is caused by fungal infections”
White spots caused by mold
White powder or spots caused by mold is less common, as this usually causes things like rust infections or other discolorations.
Two main types of mold can attack your bonsai:
Pathogenic mold is usually caused by a poor soil mix.
What typically happens in this scenario, is that leaves and other debris will drop into damp soil that has not been calibrated correctly, Mold will then form on the trunk of your bonsai and slowly work its way up to your plant.
This mold will then feed off your plant causing:
- Declaration of the leaves
- Leaves falling off
- Flowers/fruit not arriving when scheduled
- Slowed plant growth
- Drooping or wilting branches
This can also cause white spots to occur.
Non-pathogenic mold occurs in a similar way however can be more dangerous, not only to your plant but also potentially to any pets or even you.
How to avoid white spot mildew caused by mold?
To treat white spot mildew caused by mold, you would treat this in the same way as you would treat a scale infection or bug infection of any kind.
To get a full to-do list then check out my scale removal post here but to summarize:
- Remove your bonsai plant to avoid infecting other plants
- Put on a pair of gardening gloves
- Use 70% rubbing alcohol in a cotton ball swab to rub down your plant in all the hard-to-reach areas, (leaves branches, etc) removing the white spots.
- Wipe down the planter/plant pot and topsoil with rubbing alcohol in a tissue
- Mix a solution of 30oz of water, two tablespoons of liquid soap, and 1 cup of rubbing alcohol in a solution
- Pour this solution in a spray bottle
- Spray your plant thoroughly
- Leave to dry for 24 hours
Again to prevent any future infestation you will want to clean your plant like this at least once every two weeks.
A lot of mold-based infections your bonsai will have are because of overwatered soil (often the opposite problem of fungal white spots). If this is the case you may want to repot your bonsai weekly or remove any debris daily from building up.
Once again, should your plant be too far gone with mold infections, consider taking it to a specialist bonsai garden center to treat.
Why is it important to treat white spots on bonsai leaves?
White spots on bonsai leaves are important to treat as failure to do so can result in poorer health and even death for your bonsai tree. This will typically start with leaves discoloration, eventually falling off as the white spots slowly envelop the rest of your plant.
Which plants suffer from white spots?
As bonsai trees are made up of thousands of different species, are there any breeds that suffer from white powder more than others?
Chinese and Japanese Elms plants are more likely to suffer from white spots than other bonsai species. This is mainly because of the number of leaves that fall under broadleaf varieties. They also have the susceptibility they have to dry topsoil.
My top picks for the gear you will need!
So like I mentioned earlier, over the past three years of running PlantPaladin, hundreds of people have asked me for my recommendations on the best bonsai gear on the market.
Having spent thousands of dollars on bonsai items these past few years and tested at least 100 bonsai-specific products, I’ve listed my favorite products below – All of which I highly recommend and think you can get great value.
They can purchase directly by clicking the link to take them to Amazon.
Bonsai Tool Set: One of the significant challenges I’ve had is finding a toolset that was not only durable but didn’t break the bank. SOLIGT has recently developed a fantastic bonsai tool set that covers all the tools you need to trim, prune, and repot your trees. – You can grab it here.
Complete Bonsai Set: Many of you will want to grow your bonsai trees entirely from scratch, but finding the varicose seeds, pots, and other items in one place can be challenging. Leaves and Sole then have created a complete bonsai set that I’ve personally used that ticks all the boxes. You can grab it here.
Bonsai wire: The number of times I’ve run out of wire for my bonsai or purchased cheap bonsai wire that doesn’t do the job is embarrassing for me to admit. After a lot of trial and error, I found that using Hotop’s aluminum bonsai wire is one of the best options on the market. This can easily be used for both indoor and outdoor bonsai. You can grab it here.
This post was written by Fehed Nicass who has over 2 years experience